The conventional bearing support system in a steering column of an automotive vehicle comprises a hardened steel wedge on the steering shaft for supporting the inner race of a bearing, and a separate steel wave spring to back up the wedge. One common complaint is that this type of bearing support vibrates and becomes noisy over rough roads, the noise being sometimes referred to as "bearing clack". The problem becomes worse as the wedge wears.
Based on laboratory testing, the natural frequency of the steering column is believed to lie close to that of the bearing support system. This is said to cause the system to relax, allowing the wedge to back out leaving a space between the shaft and the bearing. The resulting vibration and noise becomes objectionable and accordingly an improved bearing support system is needed.
In accordance with the present invention, a spring wedge unit is provided for the bearing comprising an integral one-piece ring of flexible resilient material, preferably urethane. One end portion of the ring is in the form of a wedge which has a cylindrical radially inner surface in bearing contact with the steering shaft, and a conical radially outer surface which provides a radially inner support for the bearing.
The spring wedge unit also has an annular spring flange extending from the large end of the wedge. The spring flange is frusto-conical and is adapted to bear against an annular portion of the steering shaft. The spring flange abuts the annular portion of the steering shaft under pressure and is resiliently flexed to resist axial movement of the ring and hold the wedge portion of the ring firmly against the inner race of the bearing. In one embodiment, the conical surface of the wedge extends at an angle of about 20.degree. and the spring flange is angled at about 30.degree..
The ring also preferably includes an integral annular stop which projects radially outwardly from the large end of the wedge portion of the ring to provide an axial stop for the bearing.
It is a primary object of this invention to provide a steering column assembly having a spring wedge unit for the inner race of the bearing, which dampens vibration and suppresses noise and has the foregoing features.
Another object is to provide a steering column assembly in which the spring wedge unit of a one-piece, integral construction serving both as a wedge for the bearing and a spring back-up.
Another object is to provide a spring wedge unit for a steering column which is capable of being readily and inexpensively manufactured.